1. Field of the Invention
The invention relates to a semiconductor wafer provided with columnar electrodes used for manufacturing semiconductor devices having a size which is approximately the same as a size of a chip sliced from the wafer, which are also called chip-sized packages, and a method of the production such a semiconductor wafer. The invention also related to a semiconductor device provided with columnar electrodes and a method of manufacturing the device.
2. Description of the Related Art
FIGS. 11A to 11G illustrate a method of producing a semiconductor wafer, provided with columnar electrodes, used for manufacturing chip-sized packages. FIG. 11A shows a partially enlarged section of a semiconductor wafer 10, on which electrode terminals 12 (the drawing shows only one of them) and a passivation film 14 are formed. A material, such as polyimide, is coated on the electrode terminals 12 and the passivation film 14, and the coated film is then patterned to form an insulation layer 16 exposing the electrode terminals 12 (FIG. 11B). A conductor layer 18 is then formed to cover the exposed electrode terminals 12 and the insulation layer 16, by sputtering (FIG. 11C), which subsequently serves as an electric power supply layer for plating. A resist material is applied onto the conductor layer 18 to form a resist film, which is then patterned to form a resist pattern 20 for the formation of a wiring line pattern (FIG. 11D). Using the resist pattern 20 as a mask, the conductor layer 18 is then electrolytically plated with copper to form a patterned copper layer 22 (FIG. 11E). The patterned copper layer 22 is connected, at an end, with the electrode terminal 12 through the underlying conductive layer 18, and has a pad portion 23 at the other end, on which a columnar electrode is to be formed.
Subsequently, the resist pattern 20 is removed, and a further resist pattern 26 is formed which has openings 26a for the formation of a columnar electrode on the pad portion 23 (FIG. 11F). The film of resist pattern 26 has a thickness which is slightly larger than a height of a columnar electrode which is to be subsequently formed. A columnar electrode 24 is then formed in the opening 26a by electrolytically plating the exposed pad portion 23 with copper, the formed columnar electrode 24 having a height of the order of 100 micrometers. The columnar electrode 24 has plated films, such as plated nickel and palladium films, on its top face, which are not shown in FIG. 11F. The resist pattern 26 is then removed, and the exposed conductive layer 18 is etched and removed so as to provide a patterned wiring line 27, which consists of the copper layer 22 and the underlying conductor layer 18 (FIG. 11G).
In this way, a semiconductor wafer 10 is obtained which has, on its surface, a number of patterned wiring lines 27 which are connected with the electrode terminal 12 at one end, and has the columnar electrode 24 at the other end.
FIGS. 12A and 12B illustrate a method of encapsulating a semiconductor wafer 10, having formed columnar electrodes 24, by a resin. The semiconductor wafer 10 is placed on a lower mold 31, with the face having the columnar electrodes 24 being faced upwardly. A resin material for encapsulation 28 is supplied onto the wafer 10, and the wafer 10 is then clamped together with the resin material 28 between an upper mold 32 having an encapsulating film 30 attached to its clamping face and the lower mold 31, as shown in FIG. 12A. By this clamping, molten resin is spread over the electro-deformed face of the semiconductor wafer 10 to encapsulate it, as shown in FIG. 12B. After the encapsulation, the wafer 10 having the encapsulating film 30 attached thereto is removed from the molds 31, 32, and the film 30 is peeled from the wafer 10. Terminals for mounting (not shown), such as solder balls, are subsequently bonded to the top faces of columnar electrodes 24, and the semiconductor wafer 10 is then cut into individual chips to provide chip sized packages.
In the above method, the top faces of the columnar electrodes 24 are covered during the encapsulation of the semiconductor wafer 10 by the film 30 in order to prevent the encapsulating resin 28 from adhering to the top faces of the columnar electrodes 24. However, because of the uneven heights of the columnar electrodes 24, for example, the encapsulating resin may intrude into the space between the top face of the columnar electrode 24 and the encapsulating film 30 during the encapsulation, and be left on the top face of the columnar electrode 24 and adhered thereto.
The encapsulating film 30 is peeled from the encapsulated semiconductor wafer 10 after the encapsulation in order to remove the resin left on the top face of the columnar electrode by adhering the resin to the film 30. However, merely by peeling the encapsulating film 30 from the encapsulated semiconductor wafer 10, the resin left on the top face of the columnar electrode 24 is not always fully removed. The top face of the columnar electrode 24 is a bonding face for a mounting terminal, such as a solder ball, to be bonded thereto, and the resin adhered to the top face of the columnar electrode 24 raises a problem in terms of bonding of the columnar electrode 24 to the terminal. For this reason, the top face of the columnar electrode 24 is cleaned after peeling off the encapsulating film 30 by, for example, blasting.
However, the resin left on the top face of the columnar electrode 24 cannot always be fully removed even by such cleaning, and excessive cleaning to completely remove the resin from the top face of the columnar electrode 24 raises problems such as adverse deterioration of the encapsulating resin.
As such, in the conventional method of producing a semiconductor wafer provided with columnar electrodes, there has been a problem that an encapsulating resin is left on the top faces of the columnar electrodes to thereby prevent bonding of the columnar electrodes to mounting terminals.